Enhance the mechanical performance of polyacrylamide hydrogel by aluminium-modified colloidal silica

Polyacrylamide (PAM)–silica nanocomposite hydrogels with enhanced mechanical performance were synthesized by in situ polymerization of acrylamide in the presence of colloidal silica nanoparticles. Two kinds of silica particle dispersions with different surface properties, CAL25 and 30R25, were used as models. The former is stabilized by aluminium while the latter by sodium. The compressive stress-strain measurements showed that CAL25 significantly enhanced the mechanical performance of PAM hydrogels while 30R25 only had marginal effect. This difference was attributed to different particle–polymer interactions and confirmed by adsorption behaviours of PAM on these two colloidal silica particles and rheological measurements, which suggested that CAL25 interacted much stronger with PAM. Aluminium was identified as the main reason contributing to stronger interactions between PAM and CAL25 particles.